1. Field of the Invention
This invention relates to a small slider unit having a slide table moving along a rail.
2. Description of the Related Art
This type of slider units is conventionally known from, for example, FIG. 12 in Japanese Patent No. 3927285. Such a slider unit includes a slide table moving on a rail fixed to a mounting base, and position detection means for detecting the position of the moving slide table. The position detection means of the slider unit is made up of, for example, a proximity sensor or a photosensor which is fixed to a mounting base, and a dog (i.e., a detection element) attached to the slide table to cause the sensor to detect the slide table.
In the slider unit comprising such position detection means, when the dog comes near the sensor, the position of the slide table is detected, so that, for example, the slide table can be stopped at the stroke end or the zero point adjustment can be performed for alignment of the slide table.
Such a slider unit as described above is used in various situations. For conveyance of a very-small work piece, the slider unit is required to be correspondingly reduced in size.
For example, when the slider unit is used to convey a semiconductor device, the size of the slide table can be significantly reduced because the work piece is very small and very light in weight.
However, in conventional slider units, the sensors are situated outside the slide table in the lateral direction (outside the movement path of the slide table), while the dogs protrudes from the slide table in the lateral direction so as to face the sensors (see FIG. 14 of in Japanese Patent No. 3927285).
Accordingly, when the slide table is reduced in size, the placement of the positional detection means unavoidably involves the problem of a limit to the reduction in size of the entire slider unit in the lateral direction.